As a continuation of our investigation of the microcirculation and related energy conversion processes in the inner ear we propose to concentrate on the physiological mechanisms that control the flow through the terminal capillaries. Through a surgical approach in the guinea pig, the organ of Corti and its blood supply through the vessel of the osseous spiral lamina and stria vascularis are exposed. The blood supply and cellular structures are clearly visualized through the microscope while blood flow and microelectrodes (oxygen sensitive and AC recording) are visually monitored on a closed circuit television screen and recorded by motion picture. Various parameters of microcirculatory control such as stimulation of sympathetic nerve supply, local CO2 build up, effect of toxins on peripheral capillary pericytes will be manipulated. The ultimate goal is to determine the factors that influence inner ear microcirculation and the effect this has on the electrochemical processes of the organ of Corti. These physiological processes are at the root of sensorineural deafness.